1. Field of the Invention
This invention relates to integrated circuits and more particularly relates to manufacturing integrated circuits.
2. Description of the Related Art
Conventionally, integrated circuits are manufactured on thick semiconductor wafers. Semiconductor wafers such as silicon and gallium arsenide are preferred materials for integrated circuits because of their electrical properties. Thick wafers are conventionally preferred for their ability to withstand the processing and handling required to manufacture integrated circuits on the semiconductor wafers. The thickness of the semiconductor wafers may be significantly reduced with little impact to the electronic behavior of the integrated circuit built on the wafers. In fact, manufacturing on thin wafers may be preferred over thick wafers due to lower cost of materials and the lower profile of the devices incorporating the integrated circuits manufactured on thin wafers. For example, smaller and more flexible devices may be manufactured on thin wafers. However, manufacturing integrated circuits on thin wafers presents problems with poor yield due to the fragility of the thin wafers.
One conventional solution for manufacturing integrated circuits on thin wafers is backgrinding the wafer as illustrated in FIGS. 1A and 1B. FIG. 1A illustrates a wafer 100 having devices 102 comprising an integrated circuit. The devices 102 are manufactured according to conventional methods on the wafer 100. After manufacturing is complete the wafer 100 is backgrinded through section 104 to reduce the thickness of the wafer 100. Although the end product is an integrated circuit on a thin wafer, a significant amount of the wafer was destroyed during the backgrinding. Thus, the cost of the integrated circuit of FIG. 1A is higher than a conventional thick wafer because the same amount of material was consumed in manufacturing and the manufacturing included additional steps compared to conventional manufacturing of integrated circuits on thick wafers.
Another conventional solution for manufacturing integrated circuits on thin wafers is through use of a carrier wafer as illustrated in FIGS. 2A and 2B. In FIG. 2A a thin wafer 202 is attached to a carrier wafer 206 through an adhesive 204. Manufacturing of integrated circuits on the thin wafer 202 is substantially similar to conventional manufacturing on thick wafers because the carrier wafer 206 provides support for the thin wafer 202. After devices 210 are manufactured on the thin wafer 202 the thin wafer 202 is released from the carrier wafer 206 as shown in FIG. 2B. Although the final product is an integrated circuit manufactured on a thin wafer, the manufacturing process is more costly due to the additional materials and processing steps involved in attaching and detaching the carrier wafer. Additionally, some conventional manufacturing processes have to be adapted to prevent early dissolution of the adhesive 204. For example, the adhesive 204 should not be exposed to high temperatures or certain chemicals. Further, additional cleaning steps may be necessary to remove residue of the adhesive 204 from the thin wafer 202.
In addition to having low profiles suitable for mobile devices, thin wafers may also allow manufacturing flexible electronics. Conventional solutions for manufacturing flexible electronics involve manufacturing devices on organic substrates such as polymers or depositing semiconductor layers on polymers. However, devices manufactured on polymers may have different electrical characteristics than devices manufactured on conventional semiconductor wafers because the electronic characteristics of the polymers or the crystal structure of semiconductors deposited on polymers are different than conventional semiconductor wafers.